The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL)1 Mission has been recently selected by ESA as the fourth medium-class Mission (M4) in the framework of the Cosmic Vision Program. The goal of ARIEL is to investigate, thanks to VIS photometry and IR spectroscopy, the atmospheres of several hundreds of planets orbiting nearby stars in order to address the fundamental questions on how planetary systems form and evolve.2

During its four-years mission, ARIEL will observe several hundreds of exoplanets ranging from Jupiter- and Neptune-size down to super-Earth and Earth-size with its 1 meter-class telescope.3 The analysis of spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets atmospheres, including the elemental composition for the most favorable targets. It will also enable the study of thermal and scattering properties of the atmosphere as the planet orbits around its parent star.